Newton's law of cooling help, please!

A murder victim has been shot through the head with a revolver. A suspect is found standing over the victim at 10:15PM holding the revolver. At 10:30PM the coroner records a body temperature of 26°C and it was also recorded that the room temperature was 21°C. An hour later a second reading of the body temperature yielded 24°C. The suspect was seen in public from 6PM to 9PM. Given that the normal body temperature of a living person is 37°C use Newton’s law of cooling to determine whether or not the suspect has an alibi.